A variety of medical conditions are treated, at least in part, by inserting a medical device into the body of an afflicted patient. For example, a stent may be used to prevent vessel occlusion, in one application, or to maintain the position of a graft used to repair tissue or disease within the body. For example, a graft may be employed to span an aneurysm within a body vessel.
Medical devices may be inserted into the body temporarily or left in the body for extended periods, even indefinitely. For example, a stent and/or graft may be implanted indefinitely within a body vessel to maintain vessel integrity, e.g., blood flow. These devices can be introduced, for example, into the esophagus, trachea, colon, biliary tract, urinary tract, vascular system or other location of a human or animal patient. For example, many treatments of the vascular system entail the introduction of a device such as a stent, catheter, balloon, wire guide, cannula, or the like, including combinations of such devices. When such devices are so used, however, body vessel walls may become damaged, possibly resulting in inflammation, thrombosis and stenosis.
To mitigate any deleterious side effects, for example thrombosis formation and stenosis, medical devices may be adapted to the biological environment in which they are used. Accordingly, medical devices may be coated with biocompatible materials. Electrostatic spinning, or “electrospinning,” is one process that may be used to apply a suitable biocompatible coating or covering to a medical device.
Electrospinning is a process for creating a non-woven network of fibers using an electrically charged solution that is driven from a source to a target with an electrical field. More specifically, a solution is driven from an orifice, such as a needle. A voltage is applied to the orifice resulting in a charged solution jet or stream from the orifice to the target. The jet forms a cone shape, termed a Taylor cone, as it travels from the orifice. As the distance from the orifice increases, the cone becomes stretched until the jet splits or splays into many fibers prior to reaching the target. The fibers are extremely thin, typically in the nanometer range. The collection of fibers on the target forms a thin mesh layer of fibrous material.
Electrospinning, however, is still a manufacturing technique in need of further development and refinement.